Sonic integrity tests
Introduction
In addition to direct methods (visual inspection, geotechnical survey, etc.), there are various indirect techniques to detect possible anomalies in deep foundations (mainly "Pile (foundation)" piles and screen modules).
Most widespread indirect methods
Sonic transparency test (ultrasonic probes)
Sonic transparency in deep foundations or sonic sounding is an ultrasonic integrity test for deep foundations and retaining elements ("Piles (foundation)" piles and screen modules mainly) of reinforced concrete. It is the most precise method that exists for detecting anomalies.
It is based on the detection of variations in the speed of propagation of a compression wave that passes through a medium through different areas. At constant distances, an increase in the propagation time corresponds to an impoverishment of its mechanical properties. The test requires prior instrumentation and preparation, consisting of the installation of steel tubes attached to the reinforcement that will be filled with water before the test.
It is carried out with portable equipment, which includes an auscultator, a depth control device and two probes, transmitter and receiver. They are introduced through the tubes, filled with water, and the signal received is recorded as they rise. The data is stored digitally for later processing.
For each pair of tubes, a diagram is obtained, which represents the propagation of the signal as a function of depth. You can use 3D visualizations, which allow you to analyze the records obtained with great precision. In the most advanced equipment, a vertical resolution of one centimeter is achieved.
Carrying out this non-destructive test by highly specialized personnel guarantees its quality and allows a preview of results to be issued on site with a first assessment of the state of the element being monitored.
Echo test (conventional hammer)
It allows the length of the element to be evaluated by measuring the time elapsed between an impact and its reflection. A sensor (usually an accelerometer) is placed on the head and hit with a conventional hammer. It must be hit on sound concrete.